The idea is to update our [parser/function.rs](https://github.com/GreptimeTeam/promql-parser/blob/main/src/parser/function.rs#L138) to a similar form of upstream: https://github.com/prometheus/prometheus/blob/main/promql/parser/functions.go#L27 So that we can use a script to keep it in sync with upstream.
The idea is to update our parser/function.rs to a similar form of upstream: https://github.com/prometheus/prometheus/blob/main/promql/parser/functions.go#L27
So that we can use a script to keep it in sync with upstream.